Democritus (Greek: Δημόκριτος) was a Greekphilosopher (born at Abdera in Thrace ca. 460 BC - died ca 370 BC). Democritus was a student of Leucippus and both believed that all matter is made up of tiny, indestructible bits which he called atoma or "indivisible units", from which we get the English word atom.